The initiation step occurs when a cell isexposed to an appropriate dose of a carcinogenicagent (the initiator) and is altered in such a way that itis likely to give rise to a tumor. Process : Rapid andirreversible and due to DNA damage (mutation)

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Promotion:

describes the step in which there isproliferation and clonal expansion of initiated cell.However, in contrast to initiator, PROMOTERS do notaffect the DNA directly and their effects are reversible.